A ligament is a piece of fibrous tissue which connects one bone to another.
Ligaments are frequently damaged (e.g., detached or torn or ruptured, etc.) as the result of injury and/or accident. A damaged ligament can cause instability, impede proper motion of a joint and cause pain.
Various procedures have been developed to repair or replace a damaged ligament. The specific procedure used depends on the particular ligament which is to be restored and on the extent of the damage.
One ligament which is frequently damaged as the result of injury and/or accident is the anterior cruciate ligament (i.e., the ACL). Looking first at FIGS. 1 and 2, it will be seen that the ACL 5 extends between the top of the tibia 10 and the bottom of the femur 15. A damaged ACL can cause instability of the knee joint and cause substantial pain and arthritis.
Numerous procedures have been developed to restore a damaged ACL through a graft ligament replacement. In general, and looking next at FIG. 3, these ACL replacement procedures involve drilling a bone tunnel 20 up through tibia 10 and drilling a bone tunnel 25 up into femur 15. In some cases the femoral tunnel 25 may be in the form of a blind hole and terminate in a distal end surface 30; in other cases the femoral tunnel 25, or an extension of the femoral tunnel 25, may pass completely through femur 15. Once tibial tunnel 20 and femoral tunnel 25 have been formed, a graft ligament 35, consisting of a harvested or artificial ligament or tendon(s), is passed up through tibial tunnel 20, across the interior of the knee joint, and up into femoral tunnel 25. Then a distal portion of graft ligament 35 is secured in femoral tunnel 25 and a proximal portion of graft ligament 35 is secured in tibial tunnel 20.
There are currently a number of different ways to secure a graft ligament in a bone tunnel. One way is to use an interference screw 40 (FIG. 4) to wedge the graft ligament against an opposing side wall of the bone tunnel. Another way is to suspend the graft ligament in the bone tunnel with a button 45 and a suture 50 (FIG. 5) or with a crosspin 55 (FIG. 6). Still another way is to pass the graft ligament completely through the bone tunnel and affix the graft ligament to the outside of the bone with a screw 60 and washer 65 (FIG. 7) or with a staple (not shown).
The “Gold Standard” of ACL repair is generally considered to be the so-called “Bone-Tendon-Bone” fixation. In this procedure, a graft of the patella tendon is used to replace the natural ACL. Attached to the opposing ends of the harvested tendon are bone grafts, one taken from the patient's knee cap (i.e., the patella) and one taken from the patient's tibia (i.e., at the location where the patella tendon normally attaches to the tibia). The graft ligament is then deployed in the bone tunnels, with one bone graft being secured in the femoral tunnel with an interference screw and the other bone graft being secured in the tibial tunnel with another interference screw. Over the years, this procedure has generally yielded a consistent, strong and reliable ligament repair. However, this procedure is also generally considered to be highly invasive and, in many cases, quite painful, and typically leaves unsightly scarring on the knee and a substantial void in the knee cap.
As a result, alternative procedures have recently been developed that incorporate the use of soft tissue grafts such as the hamstring tendon. However, soft tissue grafts such as the hamstring can be difficult to stabilize within a bone tunnel. More particularly, the use of an interference screw to aggressively wedge the hamstring against an opposing side wall of the bone tunnel can introduce issues such as graft slippage, tendon winding, tissue necrosis and tendon cutting. Furthermore, the use of a suture sling (e.g., such as that shown in FIG. 5) and/or a crosspin (e.g., such as that shown in FIG. 6) to suspend the hamstring within the bone tunnel can introduce a different set of issues, e.g., it has been found that the suture sling and/or crosspin tend to permit the graft ligament to move laterally within the bone tunnel, with a so-called “windshield wiper” effect, thereby impeding ingrowth between the graft ligament and the host bone and/or causing abrasion and/or other damage to the graft tissue. In addition, the use of a crosspin (e.g., such as that shown in FIG. 6) to secure a hamstring within the bone tunnel can introduce still other issues, e.g., difficulties in looping the hamstring over the crosspin, or tearing of the hamstring along its length during tensioning if and where the crosspin passes through the body of the hamstring, etc.